Because they heat the food from the inside out (rather than outside-in), microwave ovens have a better cooking efficiency (the % of energy that heats food during the cooking cycle) than electric or gas convection ovens. … Energy use. Oven typeEfficiencyMicrowave57%Electric convection oven17%Gas convection oven9%Microwave cooking: Does it really strip nutrients and ruin our health? www.precisionnutrition.com › all-about-microwave-cooking